Metal Removers containing Phosphates Test conducted-Please leave feedback!

My coworkers and I were not very busy at the office last week and decided to investigate the metal removers that we carry and the content of phosphates included. Here is what we found: We had five cups of tap water: #1 tested in between 500-1000 parts phosphates with nothing added; #2 had a few drops of a phosphate remover, but registered no different, probably due to the fact that we tested it too soon; #3 had a few drops of a metal removing product containing citric acid, di-phosphonic acid, etc.....my impression prior to this test is that the phosphates would be quite a bit higher than what we were getting on the tap--on the contrary, this test registered zero phosphates. To back this reading up, since I was using a low range phosphate test, and thought maybe an extremely high phosphate reading might alter true results, I diluted that cup with cup #4, majority tap water and just a little of cup #3.....I got a reading of around 300 parts. Lastly, cup #5 had a few drops of a metal remover which contained phosphonic acid...the phosphate reading was zero! Am I missing a key element, do these metal removers with this chemical have to react to the product they are chelating, or removing, before the phosphates become active, or what? I have talked to several pool professionals and chemical representatives that I know, and everyone is stumped and has no answer. Please clarify with any input! As well, if anyone has ever conducted this test and has found any different than I have, please advise.

Replies

Richard A. Falk November 13, 2009 at 1:19am

The original Best Guess CYA chart was created by Ben Powell at The PoolForum in 2003 (maybe even earlier). I modified that chart to conform to chemical theory and for additional levels to handle yellow/mustard algae here. The chlorine/CYA relationship is based on known science since at least 1974 as described in this paper though the specific algae-inhibition levels were determined through observation of hundreds and eventually thousands of pools (there are over 20,000 members at The PoolForum and over 10,000 at Trouble Free Pool, so far). Though Ben initially looked at the commercial/public pools he managed, the forums took off mostly with residential pool owners and is where we now get most of our data. I use this spreadsheet I created to calculate the active chlorine (hypochlorous acid) concentration among other things.

Commercial/public pools have unique challenges due to the much higher bather loads and some day I'd like to address those through the same methodical and science-based process that we've used to figure out how homeowners can manage their residential pools.
David Penton November 12, 2009 at 7:45am

Richard A. Falk said:
My pool has had 2000-3000 ppb phosphate levels, but I keep it algae free using only chlorine at an appropriate Free Chlorine (FC) level relative to Cyanuric Acid (CYA) as shown here. Phosphates do not "cause" algae, but they do provide an essential nutrient to algae so if you don't control algae through other means, such as an appropriate FC/CYA ratio, then the algae can grow relatively quickly (though even under ideal conditions algae only double in population every 3 to 8 hours).

Just a question...

I have never seen a chart detailing the FC/CYA ratios. Do you have a link where I could find that?

Thanks
Richard A. Falk November 12, 2009 at 12:37am

Generally, there are two broad classes of metal sequestrants on the market. The ones that are not based on phosphate, such as EDTA, aren't as strong or long-lasting. They break down with chlorine more rapidly so need more frequent dosing to keep the metal out of solution. The phosphate-based sequestrants, such as HEDP (or DEDP, phosphonic acid, or phosphonates) tend to be more efficient and break down much more slowly from chlorine or other oxidizers. When they do break down, they can release orthophosphate.

Metal sequestrants are only a short-term solution to keep metal out of solution to prevent staining. The long-term solution is to physically dilute the water, replacing it with water free of metals. This can, of course, be challenging if only well water is available though one can use a water filter (ion exchange) during the fill to remove the metals.

Phosphates do not only come from phosphate-based metal sequestrants, but are also found in some fill water. Some municipal water districts add orthophosphate as a corrosion inhibitor. Where I live, for example, the phosphate level is 300-500 ppb in the tap water. My pool has had 2000-3000 ppb phosphate levels, but I keep it algae free using only chlorine at an appropriate Free Chlorine (FC) level relative to Cyanuric Acid (CYA) as shown here. Phosphates do not "cause" algae, but they do provide an essential nutrient to algae so if you don't control algae through other means, such as an appropriate FC/CYA ratio, then the algae can grow relatively quickly (though even under ideal conditions algae only double in population every 3 to 8 hours).
Richard J. Kersey November 11, 2009 at 3:12pm

Brian Evers said:
My "guess" and in layman terms - is that all the phosphate tests out there only measure ORTHOphosphates, and since the majority of sequestering agents and cleating agents do not use this they would not register any. Also - since phosphous can bind with calcium ( ie Calciumphosphate) the sequestering agent actually locked up the parts that were in the water since you said it was tap water and most likely had calcium in it also. again, just a guess
Brian Evers September 11, 2009 at 1:32pm

My "guess" and in layman terms - is that all the phosphate tests out there only measure ORTHOphosphates, and since the majority of sequestering agents and cleating agents do not use this they would not register any. Also - since phosphous can bind with calcium ( ie Calciumphosphate) the sequestering agent actually locked up the parts that were in the water since you said it was tap water and most likely had calcium in it also. again, just a guess
Harold Evans September 2, 2009 at 7:25pm

Dear John,

To extend the comments offered by Jerry Rademan there is an additional condition that will impact orthophosphates with sequest products containing Phosphonic Acid. R. Neil Lowry Ph.D wrote an article in The Canadian show issue of Pool & Spa Marketing Magazine Vol. 27 No. 7 pg 57 Dec/03 entitled Phosphate Removal Revisited. "Pool water sequestering agents are in the main polyphosphate or phosphonic acid formulations, which as their name implies are phosphorus-based. In pool water in the presence of chlorine and sunlight, these products will hydrolyze over time and decompose in orthophosphates! It is estimated that a pool on a regular regime of sequestering agents would accumulate levels of 1-3 ppm plus over a standard pool season. Most orthophosphates found in pool water originate from stain and scale control formulations." Additionally look at the test kit manufacturers recommendations for desirable levels of ortho phosphate to prevent algae growth. We are not testing polyphosphates in the pool industry but rather ortho. So if polyphosphates are not measure with conventional test kits it gets a little confusing. Essentially the artle states that eventually they become ortho phosphates.
The additional item that will influence your test process is chlorine being along with sun light. Orenda Technologies my firm has concrete solutions also for controlling stains and controlling phosphates. This info and a video is available to view on line. I welcome your comments

Harold Evans
Orenda Technologies
www.orendatech.comn
John Dauzat September 2, 2009 at 6:02pm

Thanks, Jerry, I thought there would be some reason as to why I had no reading; everyone speaks of the phosphate introduction via most metal removers. I appreciate your input!

Jerry Rademan said:
John,

I am Jerry Rademan from HydroPure Technologies, Inc in Jacksonville, FL. We supply a non-polyphosphonic acid containg sequestering agent called Liquid MetalTrap. The reason you did not find phosphates in your testing is because the phosphonic acid needs to photo-decompose in the presence of sunlight (UV). The decomposition product is organic phosphates, however it takes days to develop, depending on how much sunlight is available.

I would encourage you to re-run those same tests by exposing the samples out in the open to maximize sunlight exposure, I would be extremely interested in seeing your results.

Thanks.

Jerry Rademan
Hydropure Technologies, Inc.

Jacksonv

Metal Removers containing Phosphates Test conducted-Please leave feedback!

My coworkers and I were not very busy at the office last week and decided to investigate the metal removers that we carry and the content of phosphat…
Jerry Rademan September 2, 2009 at 4:56pm

John,

I am Jerry Rademan from HydroPure Technologies, Inc in Jacksonville, FL. We supply a non-polyphosphonic acid containg sequestering agent called Liquid MetalTrap. The reason you did not find phosphates in your testing is because the phosphonic acid needs to photo-decompose in the presence of sunlight (UV). The decomposition product is organic phosphates, however it takes days to develop, depending on how much sunlight is available.

I would encourage you to re-run those same tests by exposing the samples out in the open to maximize sunlight exposure, I would be extremely interested in seeing your results.

Thanks.

Jerry Rademan
Hydropure Technologies, Inc.

Jacksonv